N = int(input())
C = input()
c = []
for i in C:
    c.append(i)

a = c.count("R")

count = 0
for b in c[0:a]:
    if b == "R":
        count += 1


print(a - count) N = int(input()) N int(input()) int input() input C = input() C input() input c = [] c [] for i in C:
    c.append(i) i C c.append(i) c.append c append i a = c.count("R") a c.count("R") c.count c count "R" count = 0 count 0 for b in c[0:a]:
    if b == "R":
        count += 1 b c[0:a] c 0:a 0 a if b == "R":
        count += 1 b == "R" b "R" count += 1 count 1 print(a - count) print a - count a count c = [] [] c count = 0 0 count N = int(input()) int(input()) N count += 1 1 count C = input() input() C a = c.count("R") c.count("R") a
N = int(input())
C = input()
c = []
for i in C:
    c.append(i)

a = c.count("R")

count = 0
for b in c[0:a]:
    if b == "R":
        count += 1


print(a - count)